Boston Police Commissioner William Evans and Mayor Marty Walsh were at a press conference for the announcement that Boston was reviving a gun buyback program.

Boston police formally re-launched a gun buyback program on Wednesday, after a recent wave of violence that included the fatal shootings of three men last week in Roxbury and Mattapan, as well as an incident Monday when gunfire erupted outside a gathering for one of the victims.

“We’re leaving no stone un-turned to end this violence,” said Mayor Martin J. Walsh during a news conference at police headquarters in Roxbury to announce the re-instatement of the buyback program, dubbed “Your Piece for Peace.”

Walsh said last year’s initiative took in more than 400 firearms and “raised awareness in our community about the number of guns on our streets and access that young people have to them.”

“We saw parents who found guns in and around their homes turn them in,” Walsh said. “That’s something that we didn’t always see before.’’

“If we get one gun off the street, this program’s effective,” Evans said, noting that last year’s initiative was launched after a 9-year-old Mattapan boy, Janmarcos Peña, was fatally shot in his home on Morton Street. “Those are the tragedies we want to avoid.”

City officials have said previously that last year’s buyback program never stopped, but publicity efforts about the program had largely ceased and now they are reigniting the campaign.

Participants in the buyback program who turn in working firearms to any Boston police district station will receive a $200 Visa gift card, police said. The stations will accept guns on weekdays between the hours of 9 a.m. and 4 p.m.

Guns must be delivered unloaded in clear plastic bags, and any ammunition must be delivered in a separate bag, police said. The person dropping off the gun will not be charged with illegal possession of that specific firearm, but “amnesty will not be given for any other crime.’’

Rifles and shotguns will be accepted but no gift cards will be given for them, officials said.

“We are focusing on potentially street crime guns,’’ Walsh said.

The announcement came after fatal shootings last week on Ernst Street in Roxbury, where 20-year-old Angel Oller and 28-year-old Andrew Reed were killed; and on Hosmer Street in Mattapan, where Darwin Adilas, 21, died.

On Monday afternoon, gunfire exploded outside a recreation center in Roxbury, where about 200 people had gathered to celebrate the life of Oller, who was buried earlier in the day. No one was struck during that shooting.

During Wednesday’s news conference, Evans also referenced the fatal shootings of Grisel Sanchez, a 31-year-old mother who was hit by a stray bullet last month as she walked through a city park, and the slaying in June of 16-year-old Jonathan Dos Santos, who was allegedly killed by two other teenagers as he rode his bicycle on Fuller Street.

As the officials discussed the buyback initiative, relatives of homicide victims were arriving outside police headquarters for an annual barbecue that the city holds for family members to offer encouragement and connect them with resources.

“My son is still not resting in peace, because there’s no closure,” said Larose, who hastened to add that the detective assigned to the case is “doing a really wonderful job. . . . He’s like family, because he cares.”

In addition to meeting with victims’ relatives, Walsh and Evans walked the streets behind police headquarters to speak with residents about public safety.

For residents of St. Richard Street in Roxbury, the issue of gun violence is very real. Late Tuesday night, someone opened fire on the street, sending bullets into a house with sleeping children and shattering the window of a parked van.

A woman, who lives at the home, but declined to be identified, said that her boyfriend was sitting outside of the house at the time and her children were upstairs, asleep.

“We’re all really shaken up by this,” the woman said on Wednesday before she walked away in tears. “We were all in the house. We’re innocent victims.”

Police confirmed they recovered ballistic evidence at the St. Richard scene, and that they were searching for those responsible.